The ACLU, which is concerned that the list encourages racial and ethnic profiling, is suing the TSA to force the release of details of the program, The Washington Post wrote.

Here are some of the suspicious behaviors: tightly gripping a bag, appearing disoriented and whistling.

“Airports are rich environments for the kind of stress, exhaustion, or confusion that the TSA apparently finds suspicious, and research has long made clear that trying to judge people’s intentions based on supposed indicators as subjective or commonplace as these just doesn’t work,” Hugh Handeyside, a staff attorney with the ACLU’s National Security Project, said in a statement.